CD4 cell counts

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What CD4 cells do

CD4 cells,
sometimes also called T-cells, or T-helper cells, are white blood cells which
organise the immune system’s response to bacterial, fungal and viral
infections.

CD4 cell counts in people without HIV

A normal CD4 cell
count in an HIV-negative man is between 400 and 1600 per cubic millimetre of
blood (but doctors normally just give a figure, e.g. 500). CD4 cell counts in
HIV-negative women tend to be a little higher, between 500 and 1500.

Even if you don’t
have HIV, many factors can affect your CD4 cell count. For example, it’s known
that:

Women
have higher CD4 cell counts than men (by about 100).

Women’s
CD4 cell counts go up and down during the menstrual cycle.

Oral
contraceptives can lower a woman’s CD4 cell count.

Smokers
tend to have higher CD4 cell counts (by about 140).

CD4
cell counts fall after rest – by as much as 40%.

A
good night’s sleep can mean that you have a lower CD4 cell count the following
morning, but a higher CD4 cell count the next afternoon.

Physical
activity can affect CD4 cell counts.

None of these
factors seem to make any difference to how well your immune system can fight
infections.

Only a small proportion
of your body’s CD4 cells are in the blood. The rest are in the lymph nodes and
tissue. Variations in CD4 cell counts might be due to the movement of CD4 cells
between blood and tissue.

CD4 cell counts in people with HIV

Soon after
infection with HIV, your CD4 cell count probably dropped sharply, before
stabilising at around 500 to 600. Even while you are well and have no
obvious symptoms of HIV, millions of your CD4 cells are becoming infected by
HIV and millions more are produced to replace them.

However, without
treatment, most people will not be able to make enough new CD4 cells to replace
those lost because of HIV. It’s estimated that without treatment, an
HIV-positive person’s CD4 cell count drops by about 45 every six months, with
greater falls experienced by people with higher CD4 cell counts at the time
they became HIV positive.

A CD4 cell count
between 200 and 500 indicates that some damage to your immune system has
occurred – more than the normal ups and downs of CD4 cell counts. Steeper falls
in CD4 cell counts are experienced the longer you have had HIV, and more significant
damage is done to your immune system. This means you are at greater risk of
becoming ill because of HIV.

A CD4 cell count
of below 200 indicates that you are at real risk of becoming ill with an
HIV-related illness. This is why you are recommended to have your CD4 cell
count carefully monitored if it goes below 350.

It seems that
people who experience a larger drop in CD4 cell count at the start of their HIV
infection, and whose CD4 cell count stabilises at a lower level, may be at risk
of faster disease progression.

Looking at your
CD4 cell count can provide a guide for decisions about your need to start
taking HIV treatment, as well as other medicines to prevent some HIV-related illnesses.

Your CD4 cell
count can naturally fluctuate, and factors such as having a viral infection can
affect it. Don’t put too much emphasis on a single test result. Rather, look at
the trend in a number of recent CD4 cell counts.

CD4 cell percentages

Sometimes, as well
as measuring the number of CD4 cells, doctors will also assess what percentage
of all your white blood cells are CD4 cells. This is called the CD4 cell
percentage. A normal result in a person with an intact immune system is about
40%, and a CD4 cell percentage below 20% indicates the same risk of becoming
ill with an HIV-related illness as a CD4
cell count of about 200.

CD4 cell counts and HIV treatment

In the past, CD4 cell counts were used to guide decisions
about when to start HIV treatment. However we now know that all people living
with HIV can benefit from HIV treatment and that it is better to start
treatment sooner, rather than later.

Once you start taking HIV treatment, and your viral
load starts to fall, your CD4 cell count is likely to increase gradually. The
rate at which this happens can vary a lot between individuals.

During your first months taking HIV treatment, your CD4
count will continue to be monitored regularly. Nonetheless when you are taking
HIV treatment, your viral load is a more important indicator of your health and
of the effectiveness of your treatment than your CD4 cell count. After a while,
your doctor may suggest checking your CD4 cell count less often. So long as
your health is stable and your viral load remains undetectable, CD4 results are
not relevant for decisions about your treatment.

However if your viral load increased, or you had HIV-related
symptoms, then your CD4 cell count would be monitored again.

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends
checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member
of your healthcare team for advice tailored to your situation.